1. Field of the Invention
This invention relates to document imprinters, especially for ticket tags, labels and the like, and more particularly to adjusting the position of the inking roller of such an imprinter.
2. Description of the Prior Art
As the imprinter is used, the inking roller shrinks because of wear, and/or ink depletion if the roller is of the type made of microporous material impregnated with ink.
As such shrinkage occurs, the roller must be adjusted closer to the printing unit to maintain good quality printing. If the roller is adjusted to be too close to the printing unit, the latter will be overinked and smeared printing will result. If the roller is adjusted to be too far away from the printing unit, the result will be faint printing. Such defects are objectionable in the case of conventional visually readable printing, but they cannot be tolerated where the imprinter is printing OCR characters, i.e., characters which are visually readable and also automatically readable by optical character recognition equipment. The foregoing defects will result in reading errors.
One prior art form of such adjusting means for the inking roller comprises a pair of spaced eccentric cams against which the round inking roller shaft rests. The roller adjustment is made by rotating the cams so that a smaller radius thereof engages the roller shaft. Such adjustment is difficult for the user of the machine to make. For example, when the cam screws are retightened after the adjustment has been made, the retightening tends to rotate the cams away from their adjusted position. Furthermore, precisely the same adjustment must be made on both cams, which is difficult to do.